1. Field of the Invention
The present invention relates to improvements in a bearing assembly for a wheel provided with speed detecting means, that is, a bearing assembly provided with a pulser gear for detecting the number of rotations of the wheel.
2. Related Background Art
In the brakes are suddenly applied when a vehicle is running, particularly, when the vehicle is running on a snowy road or ice in wintertime, the wheels of the vehicle may be locked before the vehicle stops. If in such case, the rear wheels are locked, stability will be reduced, and if the front wheels are locked, maneuverability will be lost, and in any case, the vehicle will become a very unstable condition.
In order to prevent such a phenomenon, there is known a so-called anti-lock apparatus in which a pulser gear is fixed to a rotatable wheel rotatable with the wheel of a vehicle and the number of rotations of the wheel is sensed by a sensor to thereby control the braking force of the wheel.
Heretofore, a plurality of balls have been interposed, for example, between an outer race and an inner race which are rotalable with the wheel, and a pulser gear having concave and convex portions alternately formed circumferentially on the outer peripheral surface thereof has been mounted on the outer race, and the number of rotations of the wheel has been detected by a sensor disposed in proximity to pulser gear.
However, with a bearing whose inner race is rotated by the running of the vehicle, it is impossible in the above-described method to measure the speed of the vehicle. Also, where a seal member is used to prevent muddy water from entering into the interior of the bearing, the sliding portion (for example, the inner race) of the seal lip becomes rusty due to muddy water or the like, and this leads to the problem that the sealing effect is reduced to reduce the service life of the bearing.